Problem: $\dfrac{d}{dx}[x^9]=$
Explanation: $x^9$ is of the form $x^n$ and therefore we can apply the power rule: $\dfrac{d}{dx}[x^n]=n\cdot x^{n-1}$ $\begin{aligned} \dfrac{d}{dx}[x^{{9}}]&={9}x^{{9}-1} \\\\ &=9x^8 \end{aligned}$ In conclusion, $\dfrac{d}{dx}[x^9]=9x^8$